1. Field of the Invention
The present invention relates to the transmission of digital audio signals, particularly full frequency digital audio signals.
2. Background Art
The telephone provides convenient audio communications worldwide. However, the frequency response of a telephone line is limited. Thus, a telephone is incapable of transmitting high fidelity or full frequency sound. While the telephone provides satisfactory communications of human speech when only the content of the speech, not the characteristics of the speech, is of interest, the telephone is unsuitable for transmission of music or professional quality audio. Additionally, the telephone requires two or more parties to be connected simultaneously and in real time. If one party is unavailable at a particular time, the other party must call again at a later time to attempt to communicate with the called party. Real time refers to the actual time during which something takes place. In this context, real time refers to conditions where the amount of time required to transmit a sound is substantially equal to the duration of the original sound, such that the transmitted sound is not of a substantially longer duration than the original sound and the transmitted sound may be reproduced with substantially no delay relative to the original sound, if simultaneous reproduction is desired.
The telephone has been inadequate for certain applications within the entertainment industry, particularly in the production of international versions of domestic entertainment materials, such as movies. For international versions to be produced, the script must be translated into other languages and performers must be located to provide new soundtrack speech in the other languages. In casting these performers, it is desirable to allow domestic casting personnel to listen to auditions in foreign countries. An "audition" or "audition performance" is a trial performance by an actor to demonstrate his or her suitability or skill, and in particular his or her vocal and verbal suitability or skill. To adequately evaluate the performers, the casting personnel need to hear high-fidelity full frequency sound. At times, casting personnel may wish to listen to and direct the auditions in real time from various distant locations. At other times, however, casting personnel may wish to have the audition recorded for later listening or review. Thus, a system that allows monitoring of recorded and real time sound samples and remote casting is desirable.
Since performers are located in countries geographically remote from the casting personnel, it has been difficult for casting personnel to attend performances or participate in recording studio sessions. Listeners have had to travel to distant lands to direct and evaluate a performance, then travel back to their homeland. This involves much time and expense. To avoid such extensive travel, the mailing or transportation of audio recordings of the performances have been used as alternatives. However, the shipment of audio recordings is slow and their use often inconclusive, requiring additional recordings to be made and shipped. Thus, a system that allows listening to a performance from a remote location at a base location or some other remote location is desirable.
It is also useful for the remote auditioning locations to be able to hear stock sound samples for comparison with the auditioning performers. These sound samples may be compared with audition materials to help casting personnel make the best actor selection. Comparison may be accomplished both audibly and visually using integrated software of a type well known in the art, for example, SoundEdit Pro, manufactured by Macromedia of San Francisco, Calif., that converts audio signals into printable or displayable graphic voice patterns. Since stock sound samples may constitute large amounts of information, it may be difficult to transport them in a portable form. Thus, it is desirable to provide a method of communicating with a fixed data base of stock sound samples.
In the past, it was necessary to make tape recordings of performances and ship the tapes to the desired listener. Tapes provide high fidelity recording and do not require the listener to be present in real time, i.e., at the time the performance is given. However, tapes also do not allow the listener to listen in real time if desired. There is a substantial delay between performance and listening while the tapes are being transported. No realtime dialog between the performer and the listener is possible with tape recordings. The listener cannot make comments to the performer during the performance or between performances. Moreover, this method also results in substantial shipping costs.
Alternatively, if many performances are planned or if a lengthy performance is expected, the listener would often travel to the remote site and attend the performance in person. This approach avoids any impairment of sound quality by transmission media and allows realtime listening, but requires costly and time-consuming travel by important personnel.
Production of entertainment materials that include soundtrack materials from remote locations has also been difficult. One example of such a situation might involve the inclusion of the voice of an actor in Germany in an entertainment program or promotional message produced in France. In such a case, the actor's voice would have to be recorded on high fidelity media, such as magnetic tape, which would have to be transported from Germany to France. As in the case of casting, a substantial delay occurs and shipping costs are incurred during transportation of the media, and no realtime interaction is possible between the actor in Germany and the production personnel in France.